Method for transmitting an FSOC supervisor channel

ABSTRACT

Aspects of the disclosure provide for a method of transmitting state information using free-space optical communication. The method includes using one or more processors of a first communication device to collect state information of the first communication device. A supervisor signal that carries the state information is transmitted from the first communication device along with a beacon beam in a first solid angle. The supervisor signal is a frequency different from the one or more frequencies of the beacon beam. When a communication link is established between the first communication device and a second communication device, a plurality of data packets is transmitted from the first communication device to the second communication device in a second solid angle smaller than the first solid angle. A subset of the plurality of data packets that do not carry client data carries the state information of the first communication device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 16/256,478, filed Jan. 24, 2019, which is allowed, whichapplication is a continuation of U.S. patent application Ser. No.15/959,805, filed Apr. 23, 2018, now U.S. Pat. No. 10,225,006, issued onMar. 5, 2019, the disclosures of which are incorporated herein byreference.

BACKGROUND

Communication terminals may transmit and receive optical signals throughfree space optical communication (FSOC) links. In order to accomplishthis, such terminals generally use acquisition and tracking systems toestablish the optical link by pointing optical beams towards oneanother. For instance, a transmitting terminal may use a beacon laser toilluminate a receiving terminal, while the receiving terminal may use aposition sensor to locate the transmitting terminal and to monitor thebeacon laser. Steering mechanisms may maneuver the terminals to pointtoward each other and to track the pointing once acquisition isestablished. A high degree of pointing accuracy may be required toensure that the optical signal will be correctly received.

BRIEF SUMMARY

Aspects of the disclosure provide for a method of transmitting stateinformation using free-space optical communication. The method includesusing one or more processors of a first communication device to collectstate information of the first communication device and transmit, usinga beacon transmitter of the first communication device, a beacon beamand a supervisor signal in a first solid angle. The beacon beam is oneor more first frequencies, and the supervisor signal is a secondfrequency different from the one or more first frequencies and carriesthe state information. When a communication link is established betweenthe first communication device and a second communication device, acommunication link transmitter of the first communication device may beused to transmit a plurality of data packets to the second communicationdevice in a second solid angle smaller than the first solid angle. Afirst subset of the plurality of data packets carries client data, and asecond subset of the plurality of data packets carries the stateinformation of the first communication device.

In one example, the method also includes performing an adjustment of thesecond communication device using the state information of the firstcommunication device. Performing the adjustment of the secondcommunication device optionally includes updating a pointing directionof the second communication device based on a location or pointingdirection included the state information of the first communicationdevice. In addition or alternatively, performing the adjustment of thesecond communication device includes updating transmissionspecifications based on system requirements included in the stateinformation of the first communication device.

In another example, the method also includes receiving state informationfrom the second communication device and performing an adjustment of thefirst communication device using the state information of the secondcommunication device. The one or more first frequencies are optionally150 Hz or less and the second frequency is greater than 150 Hz. In anadditional example, the first solid angle covers an angular area on theorder of a square milliradian, and the second solid angle covers anangular area on an order of one hundredth of a square milliradian. Themethod additionally or alternatively includes switching, by the one ormore processors, to transmitting state information in the supervisorsignal using the beacon transmitter when the communication link is lost.

Other aspects of the disclosure provide for a system for transmittingstate information using free-space optical communication. The systemincludes a beacon transmitter configured to transmit a beacon beamincluding one or more first frequencies in a first solid angle and acommunication link transmitter configured to transmit a plurality ofdata packets. In addition, the system includes one or more processorsconfigured to collect state information of a first communication deviceand transmit, using the beacon transmitter, supervisor signal along withthe beacon beam in the first solid angle. The supervisor signal is asecond frequency different from the one or more first frequencies andcarries the state information. The one or more processors are alsoconfigured to transmit, using the communication link transmitter of thefirst communication device, the plurality of data packets to the secondcommunication device in a second solid angle smaller than the firstsolid angle when a communication link is established between the firstcommunication device and a second communication device. A first subsetof the plurality of data packets carries client data, and a secondsubset of the plurality of data packets carries the state information ofthe first communication device.

In one example, the one or more processors are further configured toperform an adjustment of the second communication device using the stateinformation of the first communication device. The one or moreprocessors optionally are configured to perform the adjustment of thesecond communication device by updating a pointing direction of thesecond communication device based on a location or pointing directionincluded in the state information of the first communication device.Additionally or alternatively, the one or more processors are configuredto perform the adjustment of the second communication device by updatingtransmission specifications based on system requirements included in thestate information of the first communication device.

In another example, the one or more processors are also configured toreceive state information from the second communication device andperform an adjustment of the first communication device using the stateinformation of the second communication device. The one or moreprocessors are also optionally configured to switch to transmitting thestate information in the supervisor signal using the beacon transmitterwhen the communication link is lost.

Further aspects of the disclosure provide for a non-transitory, tangiblecomputer-readable storage medium on which computer readable instructionsof a program are stored. The instructions, when executed by one or moreprocessors, cause the one or more processors to perform a method. Themethod includes collecting state information of a first communicationdevice and transmitting, using a beacon transmitter of the firstcommunication device, a beacon beam and a supervisor signal in a firstsolid angle. The beacon beam is one or more first frequencies, and thesupervisor signal is a second frequency different from the one or morefirst frequencies and carries the state information. The method alsoincludes transmitting, using a communication link transmitter of thefirst communication device, a plurality of data packets to the secondcommunication device in a second solid angle smaller than the firstsolid angle when a communication link is established between the firstcommunication device and a second communication device. A first subsetof the plurality of data packets carries client data, and a secondsubset of the plurality of data packets carries the state information ofthe first communication device.

In one example, the method also includes performing an adjustment of thesecond communication device using the state information of the firstcommunication device. The method also optionally includes performing theadjustment of the second communication device by updating a pointingdirection of the second communication device based on a location orpointing direction included the state information of the firstcommunication device. Additionally or alternatively, the method includesperforming the adjustment of the second communication device by updatingtransmission specifications based on system requirements included in thestate information of the first communication device.

In another example, the method also includes receiving state informationfrom the second communication device and performing an adjustment of thefirst communication device using the state information of the secondcommunication device. The method additionally or alternatively includesswitching to transmitting state information in the supervisor signalusing the beacon transmitter when the communication link is lost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram 100 of a first communication device and asecond communication device in accordance with aspects of thedisclosure.

FIG. 2 is a pictorial diagram of a network 200 in accordance withaspects of the disclosure.

FIG. 3 is a flow diagram 300 in accordance with aspects of thedisclosure.

FIG. 4 is another flow diagram 400 in accordance with aspects of thedisclosure.

DETAILED DESCRIPTION Overview

The technology relates to transferring state information betweencommunication terminals in a communications system concurrently witheither a beacon signal or a communication signal. Before a communicationlink between two communication terminals has been established, a beaconsignal may be optically transmitted with a supervisor signal thatcarries state information encoded on it. Based on the state information,an adjustment may be made to the communication device of a givencommunication terminal. Once a communication link is established, stateinformation may be optically transmitted in idle frames in thecommunication signal.

The features described herein may provide an optical communicationsystem that quickly establishes, maintains, and reestablishescommunication links. Transmitting state information of a givencommunication terminal with a beacon signal allows for anothercommunication terminal that receives the state information to preparefor establishing a communication link with the given communicationterminal earlier under coarsely aligned conditions. The received stateinformation may also allow the other communication terminal to moreaccurately determine where to point in order to establish acommunication link with the given communication terminal. After acommunication link is established, the given communication terminal maytransmit state information in idle frames in a communication signal,which may allow for quicker updates to the alignment of the othercommunication terminal with the given communication device.

Example Systems

FIG. 1 is a functional diagram 100 of a first communication device of afirst communication terminal configured to form one or more links with asecond communication device of a second communication terminal, forinstance as part of a system such as a free-space optical communication(FSOC) system. For example, a first communication device 102 includesone or more processors 104, a memory 106, a transmitter 112, a receiver114, and a steering mechanism 116.

The one or more processors 104 may be any conventional processors, suchas commercially available CPUs. Alternatively, the one or moreprocessors may be a dedicated device such as an application specificintegrated circuit (ASIC) or other hardware-based processor, such as afield programmable gate array (FPGA). Although FIG. 1 functionallyillustrates the one or more processors 104 and memory 106 as beingwithin the same block, it will be understood that the one or moreprocessors 104 and memory 106 may actually comprise multiple processorsand memories that may or may not be stored within the same physicalhousing. Accordingly, references to a processor or computer will beunderstood to include references to a collection of processors orcomputers or memories that may or may not operate in parallel. The oneor more processors 104 may be used to collect and monitor stateinformation of the first communication device 102. The state informationmay include, for example, a power level, pointing direction, geographiclocation, system requirements, or other type of information about theoperation of the first communication device.

Memory 106 may store information accessible by the one or moreprocessors 104, including data 108, and instructions 110, that may beexecuted by the one or more processors 104. The memory may be of anytype capable of storing information accessible by the processor,including a computer-readable medium such as a hard-drive, memory card,ROM, RAM, DVD or other optical disks, as well as other write-capable andread-only memories. The system and method may include differentcombinations of the foregoing, whereby different portions of the data108 and instructions 110 are stored on different types of media. In thememory of each communication device, such as memory 106, the stateinformation or updates to the state information collected by the one ormore processors 104 may be stored.

Data 108 may be retrieved, stored or modified by the one or moreprocessors 104 in accordance with the instructions 110. For instance,although the system and method is not limited by any particular datastructure, the data 108 may be stored in computer registers, in arelational database as a table having a plurality of different fieldsand records, XML, documents or flat files. The data 108 may also beformatted in any computer-readable format such as, but not limited to,binary values or Unicode. By further way of example only, image data maybe stored as bitmaps comprised of grids of pixels that are stored inaccordance with formats that are compressed or uncompressed, lossless(e.g., BMP) or lossy (e.g., JPEG), and bitmap or vector-based (e.g.,SVG), as well as computer instructions for drawing graphics. The data108 may comprise any information sufficient to identify the relevantinformation, such as numbers, descriptive text, proprietary codes,references to data stored in other areas of the same memory or differentmemories (including other network locations) or information that is usedby a function to calculate the relevant data.

The instructions 110 may be any set of instructions to be executeddirectly (such as machine code) or indirectly (such as scripts) by theone or more processors 104. For example, the instructions 110 may bestored as computer code on the computer-readable medium. In that regard,the terms “instructions” and “programs” may be used interchangeablyherein. The instructions 110 may be stored in object code format fordirect processing by the one or more processors 104, or in any othercomputer language including scripts or collections of independent sourcecode modules that are interpreted on demand or compiled in advance.Functions, methods and routines of the instructions 110 are explained inmore detail below.

The one or more processors 104 may be in communication with thetransmitter 112 and the receiver 114. Transmitter 112 and receiver 114may be part of a transceiver arrangement in the communication device102. The one or more processors 104 may therefore be configured totransmit, via the transmitter 112, data in a signal, and also may beconfigured to receive, via the receiver 114, communications and data ina signal. the received signal may be processed by the one or moreprocessors 104 to extract the communications and data.

The transmitter 112 may be configured to output a beacon beam 20 thatallows one communication device to locate another. The transmitter 112may include a beacon transmitter The beacon beam may be output at awider angle than the optical communication beam, allowing acommunication device that receives the beacon beam to better locate thebeacon beam. In other words, the beacon beam may cover a larger solidangle in space than the communication signal. For example, the beaconsignal may cover an angular area on the order of a square milliradian,and the communication signal may cover an angular area on the order of ahundredth of a square milliradian.

The transmitter 112 may also be configured to transmit a communicationsignal over a communication link 22. In some examples, the communicationsignal may be a signal configured to travel through free space, such as,for example, a radio-frequency signal or optical signal. The transmitter112 may include one or more communication link transmitters that areseparate from the beacon transmitter. Alternatively, the transmitter 112may include one transmitter configured to output both the beacon beamand the communication signal. In some implementations, a givencommunication link transmitter may include a semi-conductor device, suchas, for example, a light-emitting diode (LED) or a laser diode. In someexamples, the given communication link transmitter may include a fiberlaser or a solid state laser. Laser diodes may be directly modulated, orin other words, the light output may be controlled by a current applieddirectly to the given communication link transmitter. The givencommunication link transmitter may include a single-mode laser diodethat supports one optical mode, or the given communication linktransmitter may include a multimode laser diode that supportsmultiple-transverse optical modes. The given communication linktransmitter may receive a modulated communication signal from amodulator (not shown), which modulates a received electrical signal. Thegiven communication link transmitter may then convert the modulatedelectrical signal into an optical communication beam that is configuredto establish a communication link with another communication device, andthen output the optical communication beam from the first communicationdevice 102.

The transmitter 112 of the first communication device 102 may also beconfigured to output a beacon beam 20 a to establish a communicationlink 22 a with the second communication device 122, which receives thebeacon beam 20 a. The first communication device 102 may align thebeacon beam 20 a co-linearly with the optical communication beam (notshown) that has a narrower solid angle than the beacon beam and carriesa communication signal 24. As such, when the second communication device122 receives the beacon beam 20 a, the second communication device 122may establish a line-of-sight with the first communication device 102 orotherwise align with the first communication device. As a result, thecommunication link 22 a that allows for the transmission of the opticalcommunication beam (not shown) from the first communication device 102to the second communication device 122 may be established.

The receiver 114 may include a tracking sensor configured to detect theoptical beam and an optical fiber. In addition, the receiver 114 mayalso include a lens, mirror, or other system configured to divert aportion of a received optical beam to the tracking sensor and allow theremaining portion of the received optical beam to couple with theoptical fiber. In some examples, the tracking sensor includes, but isnot limited to, a position sensitive detector (PSD), a charge-coupleddevice (CCD) camera, a focal plane array, a photodetector, a quad-cell,or a CMOS sensor. The tracking sensor may detect a signal location atthe tracking sensor and may convert the received optical beam into anelectric signal using the photoelectric effect. The tracking sensor maytrack the received optical beam, which may be used to direct thesteering mechanism 116 to counteract disturbances due to scintillationand/or platform motion.

The one or more processors 104 may be in communication with the steeringmechanism 116 (such as a mirror or a gimbal) for adjusting the pointingdirection of the transmitter 112, receiver 114, and/or optical beam. Inparticular, the steering mechanism 116 may be a MEMS 2-axis mirror,2-axis voice coil mirror, or piezo electronic 2-axis mirror. Thesteering mechanism 116 may therefore be configured to steer thetransmitter, receiver, and/or optical beam in at least two degrees offreedom, such as, for example, yaw and pitch. The adjustments to thepointing direction may be made to establish acquisition and connectionlink, such as communication link 22, between the first communicationdevice 102 and the second communication device 122. In addition, theadjustments may optimize transmission of light from the transmitterand/or reception of light at the receiver. In some implementations, theone or more processors 104 may provide closed loop control for thesteering mechanism 116 to adjust pointing direction based upon theoptical beam received over the communication link from a transmittingcommunication device, such as an optical beam received over thecommunication link 22 b from the second communication device 122.

Similarly, the second communication device 122 includes one or moreprocessors, 124, a memory 126, a transmitter 132, and a receiver 134.The one or more processors 124 may be similar to the one or moreprocessors 104 described above. Memory 126 may store informationaccessible by the one or more processors 124, including data 128 andinstructions 130 that may be executed by processor 124. Memory 126, data128, and instructions 130 may be configured similarly to memory 106,data 108, and instructions 110 described above. In addition, thetransmitter 132, the receiver 134, and the steering mechanism 136 of thesecond communication device 122 may be similar to the transmitter 112,the receiver 114, and the steering mechanism 116 described above.

Like the transmitter 112, transmitter 132 may be configured to outputboth an optical communication beam and a beacon beam. For example,transmitter 132 of the second communication device 122 may output abeacon beam 20 b to establish a communication link 22 b with the firstcommunication device 102, which receives the beacon beam 20 b. Thesecond communication device 122 may align the beacon beam 20 bco-linearly with the optical communication beam (not shown) that has anarrower solid angle than the beacon beam and carries anothercommunication signal. As such, when the first communication device 102receives the beacon beam 20 a, the first communication device 102 mayestablish a line-of-sight with the second communication device 122 orotherwise align with the second communication device. As a result, thecommunication link 22 b, that allows for the transmission of the opticalcommunication beam (not shown) from the second communication device 122to the first communication device 102, may be established.

Like the receiver 114, the receiver 134 may include a tracking sensorconfigured to detect the optical beam and an optical fiber with the sameor similar features as described above with respect to the receiver 114.In addition, the receiver 134 may also include a lens, mirror, or othersystem configured to divert a portion of a received optical beam to thetracking sensor and allow the remaining portion of the received opticalbeam to couple with the optical fiber. The tracking sensor of receiver134 may track the received optical beam, which may be used to direct thesteering mechanism 136 to counteract disturbances due to scintillationand/or platform motion.

The one or more processors 124 may be in communication with the steeringmechanism 136 (such as a mirror or a gimbal) for adjusting the pointingdirection of the transmitter 132, receiver 134, and/or optical beam, asdescribed above with respect to the steering mechanism 116. Theadjustments to the pointing direction may be made to establishacquisition and connection link, such as communication link 22, betweenthe first communication device 102 and the second communication device122. In addition, the one or more processors 124 may provide closed loopcontrol for the steering mechanism 136 to adjust pointing directionbased upon the optical beam received over the communication link from atransmitting communication device, such as an optical beam received overthe communication link 22 a from the first communication device 102.

As shown in FIG. 1, the communication links 22 a and 22 b may be formedbetween the first communication device 102 and the second communicationdevice 122 when the transmitters and receivers of the first and secondcommunication devices are aligned. Using the communication link 22 a,the one or more processors 104 can send communication signals to thesecond communication device 122. Using the communication link 22 b, theone or more processors 124 can send communication signals to the firstcommunication device 102. In some examples, it may be sufficient toestablish one communication link 22 between the first and secondcommunication devices 102, 122, which allows for the bi-directionaltransmission of data between the two devices. The communication links 22in these examples are FSOC links. In other implementations, one or moreof the communication links 22 may be radio-frequency communication linksor other type of communication link capable of travelling through freespace.

As shown in FIG. 2, a plurality of communication devices, such as thefirst communication device 102 and the second communication device 122,may be configured to form a plurality of communication links between aplurality of communication terminals and form a network 200. Forexample, the communication terminals in network 200 includes twoland-based datacenters 205 a and 205 b (generally referred to asdatacenters 205), two ground terminals, or ground stations, 207 a and207 b (generally referred to as ground stations 207), and four airbornehigh altitude platforms (HAPs) 210 a-210 d (generally referred to asHAPs 210). As shown, HAP 210 a is a blimp, HAP 210 b is an airplane, HAP210 c is a balloon, and HAP 210 d is a satellite. Arrows shown between apair of communication terminals represent possible communication links220, 222, 230-237 between the communication terminals.

The configuration of network 200 as shown in FIG. 2 is illustrativeonly, and in some implementations the network 200 may include additionalor different communication terminals. For example, in someimplementations, the network 200 may include additional HAPs, which maybe balloons, blimps, airplanes, unmanned aerial vehicles (UAVs),satellites, or any other form of high altitude platform, additionalground communication terminals, or other types of communicationterminals. In alternate implementations, the network 200 is aterrestrial network comprising a plurality of communication devices on aplurality of ground communication terminals. The network 200 may be anFSOC network that includes communication terminals having communicationdevices equipped to perform FSOC, such as the first communication device102 and the second communication device 122. In other implementations,the network 200 may additionally or alternatively be equipped to performother forms of communication, such as radiofrequency communications.

In some implementations, the network 200 may serve as an access networkfor client devices such as cellular phones, laptop computers, desktopcomputers, wearable devices, or tablet computers. The network 200 alsomay be connected to a larger network, such as the Internet, and may beconfigured to provide a client device with access to resources stored onor provided through the larger computer network. In someimplementations, HAPs 210 can include wireless transceivers associatedwith a cellular or other mobile network, such as eNodeB base stations orother wireless access points, such as WiMAX or UMTS access points.Together, HAPs 210 may form all or part of a wireless access network.HAPs 210 may connect to the datacenters 205, for example, via backbonenetwork links or transit networks operated by third parties. Thedatacenters 205 may include servers hosting applications that areaccessed by remote users as well as systems that monitor or control thecomponents of the network 200. HAPs 210 may provide wireless access forthe users, and may route user requests to the datacenters 205 and returnresponses to the users via the backbone network links.

Example Methods

The communication devices may be used to perform a method fortransferring state information in a beacon beam or a communicationchannel. As described above, state information of the firstcommunication device 102 may be collected and monitored by one or moreprocessors 104 of the first communication device. The state informationmay include, for example, a power level, pointing direction, geographiclocation, system requirements, or other type of information about theoperation of the first communication device. The state information maybe collected by, for example, receiving data from one or more componentsof a communication device, such as the transmitter or receiver,detecting or measuring physical characteristics of a communicationdevice using one or more sensors, retrieving information from thememory, or other collection means. In one implementation, the stateinformation may be transmitted with the beacon beam. In anotherimplementation, the state information may be transmitted in an idleframe of the communication channel.

In FIG. 3, flow diagram 300 is shown in accordance with some of theaspects described above that may be performed by the one or moreprocessors 104 of the first communication device 102 and/or the one ormore processors 124 of the second communication device 122. While FIG. 3shows blocks in a particular order, the order may be varied and thatmultiple operations may be performed simultaneously. Also, operationsmay be added or omitted.

At block 302, one or more processors transmit a beacon beam from a firstcommunication device, such as the one or more processors 104 and firstcommunication device 102. The beacon beam may be transmitted using atransmitter of the first communication device and may have one or morefirst frequencies. The one or more first frequencies may be, for example150 Hz or less. The beacon beam need not carry any encoded data.

At block 304, the one or more processors transmit state information ofthe first communication device while the beacon beam is transmitted. Thestate information may be transmitted in a supervisor signal having asecond frequency. The second frequency may be different from the firstfrequency. For example, the second frequency may be greater than 150 Hz.The beacon beam and the supervisor signal may be transmitted using asame transmitter of the first communication device, such as a beacontransmitter.

At block 306, the beacon beam and the supervisor signal is received at asecond communication device, such as second communication device 122.The second communication device may receive the beacon beam and thesupervisor signal at a receiver, such as receiver 134, which couples atleast a portion of the beacon beam and the supervisor signal onto anoptical fiber of the second communication device.

At block 308, the one or more processors of the second communicationdevice obtain the state information of the first communication devicefrom the supervisor signal and use the state information to determine anadjustment to the second communication device based on the obtainedstate information. The adjustment may include, for example, an updatedpointing direction of the second communication device based on apointing direction and/or geographic location of the first communicationdevice. The adjustment may alternatively or additionally include, insome examples, changing transmission specifications at the secondcommunication device based on the system requirements of the firstcommunication device or other information related to forming oroperating a communication link between the first and secondcommunication devices.

At block 310, the one or more processors of the second communicationdevice performs the determined adjustment. Performing the determinedadjustment may include moving the steering mechanism of the secondcommunication device to the updated pointing direction or changingtransmission specification of the transmitter of the secondcommunication device. At block 312, after making the determinedadjustment, a first communication link is formed between the firstcommunication device and the second communication device. The firstcommunication link may be transmitted using a communication linktransmitter. In some examples, the first communication link may be oneof a plurality of links forming a network, such a network 200. The firstcommunication link may be used to transfer data from a source locationto a destination location through the network, such as from groundstation 207 a to ground station 207 b through network 200 or clientdevices in communication with the ground stations 207 a, 207 b. In somecases, the first communication link may be unidirectional, or configuredto only transmit data from the first communication device to the secondcommunication device or vice versa. In other cases, the firstcommunication link may be bi-directional.

Optionally, the two communication devices may switch roles tocommunicate state information of the second communication device to thefirst communication device. Alternatively, both communication devicesmay simultaneously perform both transmitting and receiving of a beaconbeam and state information. The first communication device may performan adjustment to align with the second communication device in a same orsimilar way as described above. A second communication link may beformed and may be configured to transmit data in an opposite directionfrom the first communication link.

In FIG. 4, flow diagram 400 is shown in accordance with some of theaspects described above that may be performed by the one or moreprocessors 104 of the first communication device 102 and/or the one ormore processors 124 of the second communication device 122. While FIG. 4shows blocks in a particular order, the order may be varied and thatmultiple operations may be performed simultaneously. Also, operationsmay be added or omitted.

Once one or more communication links are established between twocommunication devices, one or more processors transfer data packetsbetween the two communication devices via one or more optical beams atblock 402. Each data packet may include a header or preamble and apayload. Client data may be transmitted in the payload of a first subsetof data packets from a first communication device to a secondcommunication device, such as from first communication device 102 tosecond communication device 122 or vice versa.

At block 404, one or more processors of the first communication deviceoptically transmit state information of the first communication deviceto the second communication device via the payload of a second subset ofdata packets. The second subset of data packets may include one or moreidle frames, such as one or more data packets that do not carry clientdata. At block 406, one or more processors of the second communicationdevice obtain the state information of the first communication devicefrom the idle frames and use the state information to determine anadjustment to the second communication device. The adjustments may bedetermined in a same or similar way as described above with respect toFIG. 3. At block 408, the one or more processors of the secondcommunication device perform the determined adjustment. The determinedadjustment may be performed in a same or similar way as described abovewith respect to FIG. 3.

Likewise, at block 410, state information of the second communicationdevice is also optically transmitted to the first communication devicein the one or more idle frames. At block 412, the one or more processorsof the first communication device obtain the state information of thesecond communication device from the idle frames and use the stateinformation to determine an adjustment to the first communicationdevice. At block 414, the one or more processors of the firstcommunication device perform an adjustment to align with the secondcommunication device in a same or similar way as described above withrespect to FIG. 3. Making the one or more adjustments may help tomaintain or improve the one or more communication links between thefirst and second communication devices.

If the one or more communication links are lost, the first and secondcommunication devices may switch back to transmitting state informationon the supervisor signal with the beacon beam as described above withrespect to FIG. 3.

Unless otherwise stated, the foregoing alternative examples are notmutually exclusive, but may be implemented in various combinations toachieve unique advantages. As these and other variations andcombinations of the features discussed above can be utilized withoutdeparting from the subject matter defined by the claims, the foregoingdescription of the embodiments should be taken by way of illustrationrather than by way of limitation of the subject matter defined by theclaims. In addition, the provision of the examples described herein, aswell as clauses phrased as “such as,” “including” and the like, shouldnot be interpreted as limiting the subject matter of the claims to thespecific examples; rather, the examples are intended to illustrate onlyone of many possible embodiments. Further, the same reference numbers indifferent drawings can identify the same or similar elements.

The invention claimed is:
 1. A method of transmitting state informationusing free-space optical communication, the method comprising:collecting, using one or more processors of a first communicationdevice, state information of the first communication device;transmitting, using one or more transmitters of the first communicationdevice, a beacon beam in a first solid angle; and transmitting, usingthe one or more transmitters of the first communication device, aplurality of data packets to a second communication device in a secondsolid angle smaller than the first solid angle, a first subset of theplurality of data packets carrying client data and a second subset ofthe plurality of data packets carrying the state information of thefirst communication device.
 2. The method of claim 1, further comprisingperforming an adjustment of the second communication device using thestate information of the first communication device.
 3. The method ofclaim 2, wherein performing the adjustment of the second communicationdevice includes updating a pointing direction of the secondcommunication device based on a location or pointing direction includedthe state information of the first communication device.
 4. The methodof claim 2, wherein performing the adjustment of the secondcommunication device includes updating transmission specifications basedon system requirements included in the state information of the firstcommunication device.
 5. The method of claim 1, further comprising:receiving state information from the second communication device; andperforming an adjustment of the first communication device using thestate information of the second communication device.
 6. The method ofclaim 1, wherein the first solid angle covers an angular area on theorder of a square milliradian, and the second solid angle covers anangular area on an order of one hundredth of a square milliradian. 7.The method of claim 1, further comprising, switching, by the one or moreprocessors, to transmitting state information in a supervisor signal inthe first solid angle using the one or more transmitters when thecommunication link is lost.
 8. The method of claim 7, wherein the beaconbeam has a frequency of 150Hz or less, and the supervisor signal has afrequency greater than 150Hz.
 9. A system for transmitting stateinformation using free-space optical communication, the systemcomprising: one or more transmitters configured to transmit a beaconbeam in a first solid angle and a plurality of data packets in a secondsolid angle; and one or more processors configured to: collect stateinformation of a first communication device; and transmit, using the oneor more transmitters, the plurality of data packets to a secondcommunication device, a first subset of the plurality of data packetscarrying client data and a second subset of the plurality of datapackets carrying the state information of the first communicationdevice.
 10. The system of claim 9, wherein the one or more processorsare further configured to perform an adjustment of the secondcommunication device using the state information of the firstcommunication device.
 11. The system of claim 10, wherein the one ormore processors are configured to perform the adjustment of the secondcommunication device by updating a pointing direction of the secondcommunication device based on a location or pointing direction includedin the state information of the first communication device.
 12. Thesystem of claim 10, wherein the one or more processors are configured toperform the adjustment of the second communication device by updatingtransmission specifications based on system requirements included in thestate information of the first communication device.
 13. The system ofclaim 9, wherein the one or more processors are further configured to:receive state information from the second communication device; andperform an adjustment of the first communication device using the stateinformation of the second communication device.
 14. The system of claim9, wherein the one or more processors are further configured to, whenthe communication link is lost, switch to transmitting the stateinformation in a supervisor signal in the first solid angle using theone or more transmitters.
 15. A non-transitory, tangiblecomputer-readable storage medium on which computer readable instructionsof a program are stored, the instructions, when executed by one or moreprocessors, cause the one or more processors to perform a method, themethod comprising: collecting state information of a first communicationdevice; transmitting, using one or more transmitters of the firstcommunication device, a beacon beam in a first solid angle; andtransmitting, using the one or more transmitters of the firstcommunication device, a plurality of data packets to a secondcommunication device in a second solid angle smaller than the firstsolid angle, a first subset of the plurality of data packets carryingclient data and a second subset of the plurality of data packetscarrying the state information of the first communication device. 16.The medium of claim 15, wherein the method further comprises performingan adjustment of the second communication device using the stateinformation of the first communication device.
 17. The medium of claim16, wherein the method further comprises performing the adjustment ofthe second communication device by updating a pointing direction of thesecond communication device based on a location or pointing directionincluded the state information of the first communication device. 18.The medium of claim 16, wherein the method further comprises performingthe adjustment of the second communication device by updatingtransmission specifications based on system requirements included in thestate information of the first communication device.
 19. The medium ofclaim 15, wherein the method further comprises: receiving stateinformation from the second communication device; and performing anadjustment of the first communication device using the state informationof the second communication device.
 20. The medium of claim 15, whereinthe method further comprises switching to transmitting state informationin a supervisor signal in the first solid angle using the one or moretransmitters when the communication link is lost.